1. Field of the Invention
The present invention relates to a board anchor used to mount and fasten various materials to a wall composed of a fragile material.
2. Description of the Prior Art
Conventional board anchors such as those disclosed in Japanese Utility Model Registration No. 300632, Japanese Utility Model Application Kokai No. 63-16212, and Japanese Patent Application Publication Jitsu Kai Shou No. 3-525) show a male screw provided around the shaft part, having a drill part at one end and a flange part at the other end. At the tip of said flange part is provided a turning tool engagement hole and a female screw formed hole part continuous therewith. Mounting is performed by screwing the mounting screw into the female screw formed hole part. The user only needs to screw the anchor into the board, thereby causing the drill part to form a tap drill hole in the board, whereby a separate tap drill hole step is not required. Next, the anchor is screwed into the board by screwing the male screw of the shaft part into the tap drill hole.
In the case of the conventional board anchors, however, the drill parts are formed into a flat-pyramid-shaped, flat drill cutting tool, so not only is the resistance great when boring the tap drill hole, but the tap drill hole easily becomes crooked. As a result, the board anchor is screwed crookedly into the board.